The mechanical factors involved in the etiology and progression of osteoarthrosis will be studied in vivo. The hypothesis that the initiation and progression of cartilage degeneration are two distinct changes which are closely related but separate chronologically and mechanically will be tested. The relationship of the initiation of cartilage fibrillation to the mechanical and architectural state of its underlying bony bed will be studied in a mechanically induced animal model, as well as the effects on the overlying cartilage of the stiffening of the underlying bone. The range of mechanical stimuli necessary to create articular cartilage damage will be precisely determined. Histochemical, biochemical, metabolic, densitometrical stereological and mechanical techniques will be utilized.